package com.xiaoh.nio;

import io.netty.buffer.ByteBuf;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;
import java.util.Set;

/**
 * @author xiaoh
 * @ClassName NIOServer
 * @Description TODO
 * @Date 2020/5/11 23:09
 * @Version 1.0
 */
public class NIOServer {

    public static void main(String[] args) throws Exception {
        //创建ServerSocketChannel -> ServerSocket
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

        //得到一个Selector对象
        Selector selector = Selector.open();

        //绑定一个端口666，在服务器端监听
        serverSocketChannel.socket().bind(new InetSocketAddress(6666));
        //设置为非阻塞
        serverSocketChannel.configureBlocking(false);

        //把serverSocketChannel注册到selector关心事件为OP_ACCEPT
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        //循环等待客户端连接
        while (true) {
            //这里我们等待1秒，如果没有事件发生，返回
            if (selector.select(1000) == 0) {
                System.out.println("服务器等待了1秒，无连接");
                continue;
            }

            //如果返回的>0,就获取到相关的selectionKey集合
            //1.如果返回的>0,表示已经获取到关注的事件
            //2.selector.selectedKeys() 返回关注事件的集合
            //通过selectionKeys 反向获取通道
            Set<SelectionKey> selectionKeys = selector.selectedKeys();

            //遍历Set<SelectionKey>，使用迭代器遍历
            Iterator<SelectionKey> keyIterator = selectionKeys.iterator();

            while (keyIterator.hasNext()) {
                //获取到selectorKey
                SelectionKey key = keyIterator.next();
                //根据key对应的通道发生的事件做相应的处理
                if (key.isAcceptable()) {//如果是OP_ACCEPT，有新的客户端连接
                    //给该客户端生成一个SocketChannel
                    SocketChannel socketChannel = serverSocketChannel.accept();
                    System.out.println("客户端连接成功，生成了一个socketChannel " + socketChannel.hashCode());
                    //将socketChannel设置为非阻塞
                    socketChannel.configureBlocking(false);

                    //将当前的socketChannel注册到selector,关注事件为OP_READ，同时给socketChannel关联一个Buffer
                    socketChannel.register(selector, SelectionKey.OP_READ, ByteBuffer.allocate(1024));

                }
                if (key.isReadable()) { //发生OP_READ
                    //通过key 反向获取到对应的channel
                    SocketChannel channel = (SocketChannel)key.channel();
                    // 获取到该channel关联的buffer
                    ByteBuffer buffer = (ByteBuffer)key.attachment();
                    channel.read(buffer);
                    System.out.println("from 客户端 " + new String(buffer.array()));
                }

                //手动从集合中移除当前的selectorKey，防止重复操作
                keyIterator.remove();
            }

        }
    }
}
